A unique p53 intragenic deletion flanked by short direct repeats results in loss of mRNA expression in a human esophageal carcinoma.

A 45 base pair (bp) intragenic deletion of the p53 gene from a human esophageal cancer was analyzed in detail. This deletion contained all RNA splice consensus sequences at the 3' end of intron 7, including the RNA splice branch point, the pyrimidine-rich region and the 3' splice acceptor site. Northern blotting revealed a total lack of p53 mRNA expression in this tumor. Short direct repeats (TACTG) were found at the 5' and 3' breakpoints of the deletion and it removed one complete repeat as well as the entire region between the repeats. These results suggest that a 'slipped mispairing' mechanism occurring during DNA replication may generate p53 intragenic deletion in human esophageal cancer, leading to abolished p53 mRNA expression.